1. Field of the Invention
The present invention relates to a camera loading door interlock which is simple and inexpensive, and yet which assures the proper loading/unloading sequence for a disk-type camera in which the film cartridge incorporates a dark slide which must not be opened before the camera loading door is securely closed, and which must be closed before the camera loading door is opened.
2. Description of the Prior Art
Cameras for use with disk film cartridges have been known. One example is shown in U.S. Pat. No. 4,202,614 which illustrates a camera for use with a disk film cartridge in which the cartridge dark slide is moved with the film disk. With this arrangement the film disk must be returned to an initial position in order for the dark slide to protect the film from fogging. After use, the camera is arranged to return the film to the initia1 position whereby the dark slide is also positioned to protect the film before the film loading door can be opened. With this arrangement the camera loading door must be closed before the film can be advanced, thereby opening the dark slide. However, such a camera/cartridge construction does not permit the operation of the dark slide independently of the film disk and thus does not provide the desired dark slide/door latch interlock since the dark slide is only moved when the film disk is moved. With this arrangement, it is not possible to remove a partially exposed film disk from the camera and then to reload that disk to use the remaining unexposed frames without double exposing those frames first used.
Disk cameras for use with cartridges having a dark slide movable independently of the film disk, exemplified by U.S. Pat. No. 4,309,096, are currently marketed by Eastman Kodak Company and others. These cameras are provided with a loading door which is secured in the closed position by a suitable lever-operated latch. In most such cameras, the latch-operating lever is also operatively connected to a dark-slide-engaging lever in such a manner that the dark slide is properly oriented before the latch is operated. The latch-operating lever is commonly provided with a detent which is intended to assure that the preferred dark slide orientation/latch operation sequence is maintained. However, most such detents merely consist of a spring member which is relatively easily overcome by a moderate force on the latch-operating lever. As a result, it is possible for the camera user to be able to manipulate the operating lever in such a way that the interlock between the opening and closing of the dark slide and the opening or closing of the loading door latch is defeated. This permits the door latch to be opened without ensuring that the dark slide is completely closed, or permits the dark slide to be opened before the loading door is securely closed. Thus, the user may find that one or more frames of the film disk are partially or completely fogged because the dark slide was at least partially open at the same time that the camera loading door was open.